Electrotherapeutic impulse generator



NOV. 27, 195] EM ET AL 2,576,634

ELECTROTHERAPEUTIC IMPULSE GENERATOR Filed Jan. 25, 1946 INVENTORS ANJYIOMJVMJI MEIEZZBZNDEI ATZWM Patented Nov. 27, .1951

2,576,634 ELECTROTHERAPEUTIC IMPULSE GENERATOR Anthony Nemet. and Matei Berin'dei', London, England, assignors to The Hartford National Bank and Trust Company, Hartford Conm, as.

trustee Application January 25, 1946, Serial No. 643,419 In Great Britain December 1, 1944- 1 3' Claims. This invention relates to electrical impulse generators for electro-therapeutic purposes.

Short and sharp electrical impulses have been used for treatment of the muscles for a considerable time. The desired impulse has a high positive voltage peak with a narrow base of about of a second, accompanied by a flat negative voltage of correspondingly longer duration. These are nown as Faradic impulses, and were originally generated by a magnetic interrupter commonly known as the Bristow coil. These devices, whilst producing the required impulse, have the inherent disadvantage that they have a limited lifetime due to contact failure, and even whilst they are working they are often unreliable and inconsistent due to imperfect mechanical construction. In addition to the above-mentioned disadvantages, mechanical interrupters often distort the wave-form by an additional high frequency impulse initiated bythe sparkbn the contacts.

There are a number of known electronic devices which were developed to obviate the abovementioned disadvantages and to allow greater flexibility for separate control of intensity, frequency and even wave shape. These known devices are either too complicated and expensive due mainly to the number ofvalves used", or else the wave shape produced isnot in accordance with the one described above, which is, according to experience, best suited to produce the required physiological effect.

The object of the present invention is to overcome these disadvantages and to provide'a circuit which allows greater flexibility, produces the correct wave shape andv is very simple and inexpensive to construct The. impulse generator according to the invention comprises an open core transformer with a movable iron core, means including a gridcontrolled discharge tube for supplying directcurrent to the primary of the transformer,. a tapped secondary to the transformer with a: tapchanging switch connecting the secondary to the output terminals, and a time base circuit for intermittently applying a blocking potential to the control grid of the valve. Preferably the time base circuit consists of a condenser charged by way of an adjustable resistance to the" breakdown potential of a neon tube, at which. potential the condenser discharges suddenly through the neon tube.

According to a further feature of the invention, the open core transformer comprises two primary windings arranged in series in such manner that on movement ofthe iron core to vary the intensity of the impulsesv in the secondary winding, the inductivity of the primary circuit remains unchanged.

In order that the invention maybe more readily understood, a preferred embodiment will of a tap-selector switch 6 the appropriate voltage can be applied to a full wave rectifier 8. Instead of being a switch proper, the tap-selector 6' may be only a wandering wire for adjustment of the voltage. A switch arm 7 serves as an on-off switch in the rectifier input circuit. In the arrangement shown the switch arm 1 is linked with a further switch arm l9 which serves to select the final output voltage as will be hereinafter described. Consequently the switch arm 1 may assume a number of on positions which however are electrically interconnected and equivalent and consequently the switch 1 serves simply as an on-oii switch. In addition to the main tapped secondary winding 3, the transformer I also has an auxiliary secondary winding 4 supplying heating current to the cathode of a grid-controlled discharge tube 36', which in the example shown is a pentode assumed to be of the type employed as a power valve in radio apparatus.

The output from the full wave rectifier 8 is applied to the series connection of the discharge tube 36 and the primary winding of an open core output transformer i2 having a movable iron core 21, smoothing being effected by a choke 9 and condensers IE3 and- H'. The transformer ['2 has two primary windings I3 and M arranged end to end and connected in series, the length of each winding being effectively equal tov the length. of the movable iron core. Connected in parallel with the series connection of the primary wind.- ings I3 and I4 is a condenser i5 forming with the primary windings an oscillatory circuit determining the wave-shape of the impulse to be generated. The condenser 15 is shunted by a high resistance [6 for damping purposes. Thesecondary winding I! of the transformer I 2 is provided with a number of tappings is which can be selected by the tap-selector arm is previously referred to, which is linked with the main onoff switch 1 by means indicated diagrammatically at 20. It will be noted that in the ofi position of the switch arm 1, the switch arm f9 also rests on an off contact, short-circuiting the output terminals. The course selection of the output voltage is made by the tap-selector switch [9, and, within each selected range, fine adjustment is effected by adjusting the movable core 2| which has a constant total engagement with the two primary windings l3 and It but a variable engagement with the secondary winding ll, so that adjustment of the secondary voltage by means of the movable core 28' takes-place without affecting the inductance of the primary circuit.

The control grid of the discharge tube as is connected to the cathode of the tube by way of the parallel connection of the resistance 22 and the condenser 23 and the discharge tube is normally conducting. A condenser 33 is connected between the cathode and the second grid to which the appropriate operating voltage is applied from an adjustable tapping on a potentiometer 35 which in conjunction with a resistance 34 constitutes a potential divider for the derivation of the desired voltage.

To create the impulses, the normally conducting discharge tube 36 has to be blocked intermittently and this is eifected by the use of the time-base circuit which will now be described. A condenser 24 is charged through the series connection of a fixed resistance 26 and a variable resistance 25, the charging voltage being tapped from a potential divider comprising a fixed resistance 21 and a potentiometer 28 connnected in series across the output of the rectifier 8. The applied voltage is set by means of the potentiometer 28 and the charging rate is adjusted to the desired value by means of the variable resistance 25, the resistance 25 providing a minimum fixed resistance in the charging circuit and determining the maximum charging rate. The series connection of a neon tube 29 and a choke 30 is connected across the condenser 24 and the junction between the neon tube 29 and the choke 30 is connected to the control grid of the discharge tube 36 by way of the condenser 3| and the resistance 32. e

The mode of operation of the time-base arrangement is as follows: The discharge tube 36 is normally conducting. The charging'of the condenser 24 continues until its voltage reaches the breakdown voltage of the neon tube 29. At this voltage, the condenser 24 discharges through the neon tube 29 and causes a negative blocking voltage to be applied to the control grid by way of the condenser 3| and resistance 32 so that the discharge tube 36 suddenly ceases to conduct. This induces a high voltage impulse in the secondary winding of transformer [2. The blocking bias is dissipated through the resistance 22 and the discharge tube 36 gradually becomes conducting again, and the direct current through the primary of the transformer I2 is restored. This gives rise in the secondary I! to a low oltage impulse of opposite direction to and longer duration than the high voltage impulse. Immediately after the condenser 24 has discharged through the neon tube 29, it is progressively charged again adjustment of the potentiometer 28 or 35 respectlvely.

We claim:

1. An electro-therapeutic impulse generator comprising a source of direct-current, an electron discharge tube having a control electrode, a

transformer having a helical primary winding, a. core movably arranged entirely within said primary winding and having a length less than the length of said primary winding and a secondary winding inductively coupled to only a portion of said primary winding, said primarywinding being connected in series with said electron discharge tube to said source, said secondary winding being connected to a load, a capacitance in parallel with said primary winding to form a resonant circuit therewith, and means for periodically applying a blocking potential to said control electrode, said means including a resistance, a charging condenser connected through said resistance to said source, the value of said resistance determining the charging rate of said condenser, a choke, and a glow discharge tube connected through said choke across said condenser, said condenser discharging through said glow discharge tube upon attaining the breakdown potential thereof to provide a periodic blocking potential for said electron discharge tube 2. An electro-therapeutic impulse generator comprising a source of direct-current, an electron discharge tube having a control electrode, a' transformer having a helical primary winding, a core movable entirely within said primary Winding, said core having a length less than the length of the primary winding, and a secondary winding inductively coupled to only a portion of said primary winding and means to vary coupling between said windings, said primary winding being connected in series with said electron discharge tube to said source, said secondary winding being connected to a load, a capacitance in parallel with primary winding to form a resonant circuit therewith, a damping resistance connected across said resonant circuit, and means for periodically applying a blocking potential to said control electrode, said means including an ad-, justable resistance, a charging condenser, connected through said adjustable resistance to said source, a choke, a glow discharge tube connected through said choke across said charging condenser, said charging condenser discharging through'said glow discharge .tube upon attaining the breakdown potential thereof, and capacita tive means for coupling said control electrode to the junction of said choke and said glow dis charge tube. V

3. A generator as set forth in claim 2, wherein said primary winding is constituted by apair of series connected sections and said core haswa length substantially equal to one of saidsections and wherein said secondary is inductively coupled solely to one of said sections. V

ANTHONY NEMET. MATEI BERINDEI;

REFERENCES orrnn The following references are of record in the file of this patent: I

UNITED STATES PATENTS 554,221 I Great Britain June 24; 1943 

